Acetyl migrations in a photoexcited βγ-unsaturated methyl ketone: 1,3-shift in the excited singlet state and 1,2-shift in the triplet state

Abstract

In solution, 3-acetyl-1,2,3-trimethylcyclopent-1-ene (I) undergoes a sigmatropic 1,3-acetyl shift as the major unimolecular reaction in the excited singlet state, and a (thermatically reversible) 1,2-acetyl shift with cyclopropane ring-closure as the predominant triplet state reaction.